Adding a tiny strip of glue to the battery so it doesn't slosh around in the case is not a problem.

The problem is that you need heat to open up the device itself (all that is between the battery and the hot air gun is about 1mm of glass), followed by a bath in isopropanol and lots and lots of twaddling around with tweezers and spatulas to get the old glue residue removed from both the display and the case (risking damaging either in the process), followed by really annoying meticulous work to place a new glue sheet exactly onto the case (or display) to make sure it fits again. Oh and you always risk cracking the display while removing it.